The battle between the Vikings and the West Franks in 881.
The battle fought in February 880 between the sons of the King of East Francia and the Vikings.
The battle fought in 871 between the Wessex Saxons and Danes.
Sea battle around 1000 CE between Olaf Tryggvason and Sweyn Forkbeard.
Battle between Anglo-Saxons and Vikings on British soil around 991 CE.
Visible defenses that turned into towns.